Windows 10 on iMac 2015 won't install.
I've been trying to install Windows on my 2015 iMac for the past 6 hours, using many methods. All of them lead to a black screen. This is before the installer even starts. Backlight off, hard drive active.
Order of events:
- I open BCA, load up the ISO, it partitions the drive, downloads the software. I later halted the reboot in another attempt and verified it created OSXRESERVED and BOOTCAMP partitions. OSXRESERVED correctly had everything in it.
- BCA prompts to reboot.
- Bong noise, black screen for ~5 seconds, after that backlight goes off. Hard drive stays active.
- Eventually (not sure how long, maybe 5 minutes) it falls back to booting macOS. It comes up with "you restarted your computer because of a problem".
Things I've tried:
- Using different Windows 10 builds. Initially I used a debloated 1809 which I prepared ahead of time but I also tried regular 1809, 1909, 2009, and the latest 21H1. Same result.
- Making a flash drive manually and booting off of it to get to the installer. Same result.
- Disabling System Integrity Protection. Same result.
- Waiting for over 30 minutes. It either falls back to macOS if Boot Camp was used, or doesn't do anything if selected from boot picker (the one where you hold ALT key to get into).
- Manually deploying the packed Windows 10 image (from install.wim) using winlib and Paragon NTFS (this is what the installer does before it asks you to reboot, from there onwards you are already in the deployed image). After some fidgeting with the drivers (macOS will only detect drives that are owned by its own NTFS driver), same result. I did uninstall them correctly (system extension gone).
- Shining a torch against the screen. Backlight off and nothing on screen (that I can find, I've looked for windows logo, installer title/window, progress bar, I know where they are all located). The screen is essentially off.
Things that I haven't tried that may be worth investigating (but I don't have the skills or time for):
- Something with the bless command? Can't figure out how to use it even after reading man page.
- Manually slipstreaming the drivers. This may or may not fix it, but then again nobody's needed it so far.
- Using a different program for flashing the USB stick. I've tried Etcher and copying over files with rsync after formatting.
Please help me, I've been trying to install Windows for over 6 hours now and I've searched online countless times, only to lead to either something I've already tried or nothing.
Technical details before anyone asks:
- iMac (Retina 5K, 27", Late 2015)
- 3,3 GHz 4-core Intel Core i5 CPU
- 8GB RAM
- AMD Radeon R9 M395 2GB GPU
- 2TB Fusion Drive (APFS, tried giving 250GB and 500GB, fusion drive is NOT split and is functioning correctly)
P.S. If possible I don't want to wipe this computer, only as a last alternative, as I have a lot of large files not synced with iCloud here that I'll have to move off.
